Conventional video coding standards such as MPEG-1, H.261/263/264, etc. encode video either at a given quality setting, often referred to as “fixed QP encoding,” or at a relatively constant bit rate via the use of a rate control mechanism. If, for some reason, the video needs to be transmitted or decoded at a different quality, then the data must first be decoded and then re-encoded using the appropriate setting. In some scenarios, e.g. in low-delay real-time applications, such “transcoding” may not be feasible. Similarly, conventional video coding standards encode video at a specific spatial resolution. If the video needs to be transmitted or decoded at a lower resolution, then the data must first be decoded, spatially scaled, and then re-encoded. Again, such transcoding is not feasible in some scenarios.
There is therefore a need for techniques for efficient significant coefficients coding in scalable video codecs.